urban nuclei and the geometry of streets: the emergent
TRANSCRIPT
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Urban Nuclei and the
Geometry of Streets: the Emergent Neighborhood Model
Michael Mehaffy
Sergio Porta
Nikos Salingaros
Yodan Rofe
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Contents
• The genesis of the debate: nuclei, pedestrian sheds, movement network and neighborhoods
• A typological analysis of the options
• The neighborhood is not the same as the pedestrian shed
• The emergent neighborhood
• What we design: the movement network, pedestrian sheds and sanctuary areas
• Examples
• Conclusions
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
The modern destruction of urban structure: The
neighborhood unit + the functional hierarchy of streets
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
The new urbanist model: neighborhood
unit, transit and non-hierarchical street
design
Doug Farr’s diagrams
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
The debate: the elements and their combinations
• Urban Nucleus
• Pedestrian Shed
• Neighborhood
• Urban Thoroughfare
• Local Streets
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
The centered-shielded option (CS)
• Placing the urban nuclei at
the center
• Shielded from heavy traffic
• Overlap of neighborhood
and pedestrian shed
• Static – nuclei cannot extend and join
• Disjoint between local and
district-metro movement
and economy
• Transit not congruent with land use
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Edge – Exposed (EE) option
• Joining of the movment economy with nuclei
• Separation from neighborhoods
• Pedshed fractured by heavy traffic
• Difficult to create a main
street
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Centered – Exposed (CE) option
• The traditional city
• Put into crisis by increased
car movement and the
response to transform main
streets into arterials
• Instability at low-medium
densities and high traffic
flows
• Transforms into CS or EE as a
result of traffic engineering
and planning practices
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Edged Shielded (ES) option
• Purely theoretical
• Worse of all worlds
• Communities are
disrupted by traffic
• Urban nuclei are not
connected to the
movement network
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Key Point: The neighborhood is not the same as
the pedestrian shed
• An urban nucleus is by definition the centre of its own pedestrian
shed
• Which may or may not be identifiable as a neighborhood
• Urban designers have tended to identify and attempted to fix
community by their commercial and symbolic centers and pattern
of accessibility
• Neighborhoods arise out of the spatial structure of the city:
– its inevitable discontinuities
– local administrative boundaries (sometimes arbitrary)
– basins of different social services
– the transportation network particularly major streets
– the dynamics of different populations within the city,
– etc.
• Neighborhoods are socially constructed in time and mediated by
shared patterns of use of space
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
The emergent neighborhood model
• Urban nuclei are placed in the
best location for their
development and growth
• Neighborhoods are free of the
pedestrian sheds of the nuclei
• Allowed to center on multiple
nuclei – or non commercial
uses
• Some services and shops may
locate away from the major
streets – forming minor nuclei
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Urban nuclei, main streets, and sanctuary areas: the “400-meter rule” or the quarter mile rule
• We cannot design neighborhoods
• We design:
– Pedestrian sheds
– Main streets and
sanctuary areas
• Historical cities
demonstrate remarkable similarity in the size of areas between main streets
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
The main street – sanctuary
area form is generated by a
gradual urbanization process
a. Urbanization along main roads
b. Minor streets giving access to rear areas
c. Hemmed in by new main streets
– Bisecting shortcuts
– Later may become minor
commercial streets
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
The emergent neighborhood
in the urban region
• The formation of denser development in proximity to transit service of a higher rank.
• The generation of mixed-use corridors as an outcome of contiguous urban nuclei merging along such systems.
• The aggregation of local foci along local main streets within sanctuary areas as a result of the “spill-over effect” from urban main streets.
• The continuity of a connected ecological network of linear and planar “green” elements such as parks, tree lines, boulevards, or rivers all over the urban fabric
• arrangements at intersections with main streets that maintain the critical connectivity of the system.
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Building it up…
• Main Streets
• Public transit
• Built up areas
• Natural and
landscaped
system
• The whole…
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Example 1: The Geddes
Plan of Tel-Aviv
• Sanctuary areas (Home-
blocks) roughly 200 x 300 m.
• Local streets interweave
sometimes connecting across
blocks
• Public gardens and small
public institutions at the
center of home blocks – also
attract non locals to the
interior without disturbing
• Boulevards connecting green
system with main street
system
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Example 2: Integrating the green system with the main
movement system
a. Hyde park area London
b. Portland, OR
• Bordering with a boulevard
• Joining at an angle
• Bridging
• A boulevard as a green
corridor
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Conclusions – The emergent neighborhood
• Traditional urban form finds a new synthesis based on the distinction between pedestrian shed and neighborhood
• Urban Nuclei form pedestrian sheds
• Two new terms added to determine the distance between through streets
– Sanctuary areas
– ¼ mile rule
• Together they create the field that can allow neighborhoods to emerge
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Desert Architecture and City PlanningJ. Blaustein Institutes for Desert Research, BGU
Movement for Israeli Urbanism
ʬʠʸʹʩ ʡ ʺ ́ ʣʧʺʮ ʺʥ ʩ h ʥ y ʩʲʬ ʤ ̡ ʥ hʺʤ
Conclusions – in what way is our proposal
different? Urban seeding
• Lack of clear hierarchy of communities• The relinquishing of neighborhood as a planning unit – what
is designed is the urban structure of main streets, public transit and ecological network
• A smaller scale of primarily residential sanctuary (1/4 mile instead of ½ mile)
• Integration with ecological system – still needs to be worked out so as not to interrupt urban continuity – this is the main challenge for the 21st century
• Communities may form around pedsheds, sanctuary areas, open spaces, public institutions etc.
• Urban structure does not determine – but enables community formation – urban seeding not social engineering